You hardcore Mac workstation users might want to cut the music when it’s time to start rendering your big projects if the latest Ars tale is to be believed. According to the story, Mac Pros exhibit a strange behavior when using iTunes, Quicktime or keeping USB audio interfaces plugged in:
The problem manifests as what has been described as excessive increases in power use and processor core heat when playing songs in iTunes, watching videos via Quicktime, or even when keeping USB or FireWire-based audio interfaces plugged in and active. While hardware monitors only report a small percentage of processor use, it can still cause performance decreases of up to 20 percent for other tasks.
The problem only affects all 2009 Nehalem-based Mac Pros. Strangely, booting affected Mac Pros into Windows 7 also eliminates the problems, leading one user to suspect the issue is related to power management kernel extensions.
A young hacker involved in the hackintosh scene believes the problem is related to the driver that controls newer features of the Nehalem Xeons, including SpeedStep and Turbo Boost. He generated a hacked power management kernel extension that disabled these features, which eliminated the high heat and power draw issues while playing audio. With SpeedStep disabled, however, the CPU drew more power at idle.
It might be best to wait for Apple to release a software update patch for this one, however. In the meantime, listen to your iPod.